Direct yaw moment control of front drive type electric wheelchair with free-casters

Electrical wheelchair has been used as a convenient transport device for elderly and handicapped persons. Recently, front drive type electric wheelchair has been focused on, with which handicapped person get on it from a bed easily. However, the front drive type wheelchair is difficult to run straight not only on slope but also on flat floor because of its over-steering characteristic. If wheelchair can be driven by easy stick operation, it will be a comfortable function for handicap persons. In this paper, we propose a new wheelchair control method which provides under-steering characteristic and also realizes comfortable function, i.e. driving with same easy stick operation like the traditional rear drive type wheelchair. First, dynamic model of the wheelchair is outlined. Next, yaw rate control method based on internal model control (IMC) is proposed. Finally, the effectiveness of proposed method is confirmed by driving simulations on slope.